Internal combustion engine



June 21, 1932.

A. L. RIGHTENOUR INTERNAL COMBUSTION ENGINE Filed April 2, 1928 5Sheets-Sheet l June 21, 1932. RlGHTENOUR 1,863,877

INTERNAL COMBUSTION ENGINE Filed April 2, 1928 5 Sheets-Sheet 2 flaa L.Rgi iinour @MMLM Mags.

3 5 Sheets-Sheet 3 fizz 67%: lggghienour June 21, 1932- A. L. RIGHTENOURINTERNAL COMBUSTION ENGINE Filed April 2, 1928 June 21, 1932- A. L.RIGHTE NOUR 1,863,377

INTERNAL COMBUSTION ENGINE I Filed April 2, 1928 5 Sheets-Sheet 4kjnc'enifir' Visa L-ffz' hzenoun 1 M 2 June 21, 1932. A. L. RIGHTENOURINTERNAL COMBUSTION ENGINE Filed April 2, 1928 5 Sheets-Sheet 5 PatentedJune 21, 1932 is srarss PATEN T OFFICE 1 ASA. LEE RIGHTEN'OUR, OFCHICAGO, ILLINOIS INTERNAL COMBUSTION ENGINE Application filed April 2,

operative engagement. The cam is formed with two diametrically opposedlobes having arcuate surfaces adapted to actuate the piston successivelyfor each revolution of the cam in an intake or suction stroke, acompression stroke, a firing stroke, and an exhaust or scavengingstroke. The opposed lobes are unequal in length so that the exhaustingand intake strokes are of maximum length, and substantially longer thanthe compression and firing strokes. The opposed lobes, also are shapedto vary the time and rate of movement of the piston in oppositedirections. This may be accomplished by forming the opposed cam lobes ofdifferent transverse widths, and also by off-setting one of the contactfaces on each end of the cam at a. greater distance from thelongitudinal center of the cam than its opposite face. As a result, theopposite sides of each end of the cam are formed with arcs of diiferentcurvatures. By reason of this construction, the cam causes a rapidpreliminary movement and a subse:

quent slower movement of the pistonduring the scavenging'or exhauststroke; causes the return or suction stroke to be slowly initiated andthen accelerated to a greater speed than the maximum speed of theexhaust stroke, thereby resulting in an intense suction ac.- tion;causes the compression stroke to increase in speed during its first halfand then gradually diminish to the end or firing point; and causes thefiring stroke to be more rapid than the compression stroke, and thendecrease. thereby resulting in the greatest leverage at the beginning ofthe stroke. The piston Wlll go through one complete cycle,

of movements for each completerevolution of the cam. The valves aretherefore oper- DU and means for holding the two yieldingly in ateddirectly from the cam shaft and with-' 1928. Serial No. 266,494.

out the use of special timing mechanism and gearing. F f

By providing a full exhausting stroke and a full intake stroke, theburned gases are completely expelled from the cylinder, and a large,fresh and cool charge is taken in. As a result, no portion-of-theunburned gases remains to deposit carbon in the cylinder or to causedetonation upon contact with the incoming charge, to dilute and heatthefresh charge, and to lower the compression. Provision need not bemade for taking careof high temperatures, and a relatively thinfuelmixture may be used. A high and uniform torque is obtained. By providingan actuating cam for the piston, few mechanical parts areneeded. Thus,the motor has no crankshaft, connecting rod, camshaft, connecting rodbearing, timing gears, water jacket or radiatoni i a The primary objectof the present invention resides in'the provision of a novel motor ofthe above general type having a plurality of piston and cylinder units.

if the cylinders are spaced peripherally about the motor casing, themotor will take up a great deal of space, will be cumbersome andawkward, and will be impracticable for a great many purposes, such asfarmuse.

Other important objects of the present in-- vention therefore reside intheprovision of a new and improved. motor havinga plurality of pistonand cylinder. unitsin which the units are grouped at one side of themotor casing, and having means for operating the pistons in uniformsequence. 7

A further object is to provide a novel multi-cylinder motor in which thecylinders are grouped in a portion of the motor casing, and in which thepistons are adapted to be actuated by a cam having a plurality ofperipherally spaced points in a multiple of two. corresponding inverselyto that circumferential portion of the casing occupiedby the cylinders.a r a Still another object is to provide a multi Cylinder motor of theabove characterin, which the firing strokes of the pistons, over lap sothat one of the pistons is-in a 'firing stroke at all times, therebyobtaining a uniform torque, reducing vibration, and eliminating deadcenters.

A further object is to provide a multicylinder motor of the abovecharacter in which there will be no knocking, and in which ball-bearingscan therefore be used to advanuniform pressureat all the bearing parts,

thereby avoiding knocking and hence making the use of ball bearingspracticable. 1

A further object resides'in the provision of a novel oiling system forthe motor.

A general object resides in the provision of a'novel mnlti-cylindermotor of the above general type which is simple, light and inexpensivein constructlon, which comprises a relatively small number of parts,which can be readily assembled, disassembled and repaired at arelatively small cost, and whlch is hi hly eflicient in operation andadapted to a wi e range'of uses.

Further objects and advantages will become apparent as the descriptionproceeds.

.In the accompanying drawings, Figure 1 is a' front end view of a motorembocying the features of my invention, the end plate being removed toshow the interior.

Fig. 2 is a longitudinal sectional view'of the motor taken along line 22of Fig. 1. Fig. '3 is a transverse sectional view taken along line'33ofFig. 2.

Fig. 4 is a transverse sectional View taken along line 44 of Fig. 2.

Fig. 5 is a diagrammatic view of the actuating cam for the pistons;

Fig. 6 is an enlarged sectional View of a detail taken along line 66 ofFig. 3.

Fig. 7 is an enlarged fragmentary view in front elevation of the innerend of one of the piston and cylinder units.

Fig. 8.is a fragmentary outer end view of one of the piston and cylinderunits.

Fig. '9 is an enlarged fragmentary View of a detail of the pistonretaining means. 'VVhile the invention is susceptible of variousmodifications and alternative constructions, I have shown in thedrawings and will herein describe in detail the preferred embodiment,but it'is to be understood that I do not thereby intend to limit theinvention to the specific form disclosed, but intend tocoverall'mod'ifications and alternative 0on structions falling withinthe spirit and'scope ofthe invention as expressed in the appendedclaims.

Referring more particularly to the drawings, the motor constituting theembodiment of the invention comprises a suitable casing 10 which may beof any suitable form, and which in the present instance is generallycylindrical in shape to provide a generally cylindrical cam chamber 11.The casing 10 has front and rear end walls 12 and 13 of which the frontwall 12 has a removable cover plate l t-normally held in place by meansof a plurality of bolts 15. Depending rom the body of the casing 10 andopening to the chamber 11 is a hollow base 16 which may be supported byany suitable means (not shown). In the present instance, suitable seats17 which are adapted to receive and to be secured to parts of thesupport are pro- Vided in Opposite sides of the base 16. The casing 10is suitably ribbed to provide strengdi and rigidity.

Opening in spaced relation to the cam chamber 11 are a plurality ofsuitable cylinders. Vdhile any desired plurality of cylinders may beprovided, in the present instance I have shown sixequally spacedcylinders 18, 19, 20, 21, 22 and 23 opening at their inner ends throughthe peripheral wall of the casing 10. Since these cylinders preferablyare alike in construction, but one of them will be described, andcorresponding parts of the others will be designated by like referencecharacters. Inthe preferred construction, each cylinder is formedseparately of the casing 10, and has an outer air cooled end 2 and aninner end 25. The outer end 24 is closed by a suitable head 26 adaptedto besecured thereto by means of bolts 27, and the inner end projectsthrough an opening 28 in the peripheral wall of the casing. The cylinderis mounted in position by means of a peripheral flange 29 which issuitably secured to the peripheral margin of the opening 28 Formed inthe head 26 are asuitable inlet valve 30 controlling a fuel inletpassage 31 adapted to be connected to a suitable fuel supply (notshown), and a suitable exhaust valve 32 controlling the outlet to theexhaust. The inner d the. cylinder is tapered in its outer surface atits inner'edge, as indicated at 33, to

' bring the inner ends of the cylinders closely together, and is formedin its front and rear sides with two diametrically opposed longitudinalslots 3e and 35, extending from the inner edge substantially to theperipheral wall of the casing 10.

Slidably disposed in the cylinders 18 to 23 respectively are a pluralityof suitable pistons 37. 38. 39,40 and il. Preferably, the pistons arealike in construction, and hence but one of them will be specificallydescribed, the corresponding partsv of the others however, being.designated by like reference characters. In the preferred construction,each piston is hollow, and the inner end thereofis formed with twodiametrically opposed inwardly extending projections 42 havingholesorbores43 in registration with the extending at its opposite endsthrough the 7 slots 34 and 35 is a pin 44. Two cam rollers sequence.

45 are suitably mounted on theends of the pin44 outside of the cylinder.In: the present instance, the ,camrollers 45 are mounted on ballbearings 46, and the latter are spaced from the piston by means ofspacer sleeves 47 which are secured to the pin 44, and which bearagainstthe sides of the slots'34gand 35 The parts, i. e., the piston,the pin 44, the

spacer sleeves 47 and the ball bearings 46 with the cam rollers 45 areheld in assembled relation by means of suitable nuts 48 threaded ontothe extreme ends of the pin.

The cam rollers 45 are arranged to coact with a suitable cam 49 foractuating the pistons in timed and uniform sequence. In the presentinstance, the cam 49 comprises two separate but identical plates 49a and49b rotatably mounted in spaced and coincident relation at oppositesides of the cylinders 18 to 23 for engagement with the cam rollers45.By providing a' double cam and roller mechanism for actuating thepistons, a balanced central thrust is obtained and binding is avoided.Supporting the cam plates 49a and 49b is a suitable shaft 50 from whichthe power developed by the motor is adapted to be utilized. The shaft 50is journalled in suitable ball bearings 51 and 52 secured respectivelyin bearing sleeves 53 and 54 in the end walls 12 and 13 of the casing10. -The sleeve 54 is formed'on the end of a central hub 55 whichprojects outwardlyfrom the rear end wall 13 and which defines a smallcylindrical chamber 56 opening to the chamber 11 sub stantiallyconcentrically about the shaft 50. Preferably, the cam plates 49a and495 are .formed with rearwardly extending hubs 57 and 58 keyed tooppositely flared portions 59 and 60 of the shaft 50, the hub 8 beingdisposed in the chamber 56. Suitable packing glands 61 and 62 aresecured inthe outer ends of the sleeves 53 and 54 to close the latterand to seal the bearings for the shaft 50. V 7

If a motor comprises a single piston and cylinder unit, uniformoperation can be ob-. tained by means of an actuatingcam having twospaced heads. If a motor comprises a plurality of piston and cylinderunits uniformly spaced about the entire periphery of the casing, thesame cam may be employed to operate the pistons in timed and uniformObviously each piston will move through the four strokes of a completecycle once for each complete revolution of the cam. A motor in which thepistonaud cylinder units are arranged in uniformly spaced rela-' tionsabout the entire periphery of the casing is impracticable for manypurposes, such as farm use. The primary reasons for this are that themotor is bulky and cun1bersom-e,and

cannot be mounted satisfactorily, on land vehicles, partlcularly farmVQhIClGSL In; the

present invention,,I have therefore grouped the piston and cylinderunits, in a portion of themotor casing, thereby saving in space, andproyidinga construction adaptable to a large variety of uses, includinguses in stationary plants, and in landj andair vehicles.

-. Obviously, any desired number of piston andicylinder units maybezprovided, and these may be spaced over any desired portion of thecasing, In the present instance, as recited in the foregomg, six pistonand cylinder unlts areprovided, and thesepiston and. cylinder units aregrouped-in uniformly spaced relation in the upper half of the casing10'. The :end; piston and cylinder units are each inclined axially 15from the horizontal, and

adj acentpiston and cylinder units are angularly'spaced 30?. Obviously,a cam having "but two spaced heads would not actuate the ,piston andcylinder: unitsin uniformly timed sequence sinceduring one half of onerevolutlon each point on the cam, for example the firingTpoint or theexhaust point, would move idly throughspace. Hence, I have provided acam49 having a plurality of peripherally spaced heads in a multiple of twocorrespondmg lnversely to that circumferential portion of'the casing inwhich the piston and cylinder units are'grouped. .In the presentinstance, the cam 49 is therefore provided with four heads 63,64, and 66which preferably are substantially uniformly peripherally spaced, and-ofwhich the diametrically opposed heads 63 and .65 are convenientlydesignated as firing heads, and the diametrically opposed heads 64 and66 are conveniently designated as exhausting heads. It will be evidentthat as one head leaves the last piston and cylinder unit of the group,the opposite head comes into operative relation to the first piston andcylinder unit. 'I-Ience, the piston and cylinder unitsare actuated inuniformly timed sequence, and each piston goes through a complete cycletwice for each completerevolution of the cam 49. r p

Each of the cams [63 and 65has a curved face 67 for moving each pistonout on the compression stroke, and a curved face 68 for controllingtheinovement of the piston on the firing-stroke; Each of the cams 64 and66 has a curved face 69 for moving each piston out on the exhauststroke,and a curved face 70 for controlling the inward movement of thepiston-on the intake stroke. y

Preferably, the firing cams 63 and'65 are shorter than the cams 64 and66so that a vari able stroke motor is obtained. As a result, theexhauststroke and the intake stroke are of maximum length sofas tocompletely exhaust the gases of combustion and to take in a 'freshcool.and undiluted charge of fuel. The advantages ofthis construction'arenumerous: First, the deposition of carbon and detonations, whichordinarily occur through contact between the; fresh incoming fuel till -charge: and theunexpelled gases of combustion,-areavoided. -A-Inore dilute fuel charge may'be' used, and "still complete and-'efiicientcombustion will be obtained. -As a result, there will be no partiallybur'ned gases 'and poisons such as carbon monoxide, to' be exhaustedinto the atmosphere. Since no inert gases with the temperature'ofexhaust are presentatthe start of the intakestroke, undesirable hightemperatures are avoided. The variable stroke-also kills vibration.

Preferably, the cam faces 67,- 68, '69 and 7O are so shaped that maximumefiiciencyisobtained in combustion and in'the mechanical development ofthe power generated. :In the present instance, the cam faces are soshaped that on the exhaust stroke the piston has a rapid preliminarymovement and then a subsequent slow movement, on the inlet stroke themovement of the piston is initiated slowlyand is then accelerated to aspeed greater than the maximum speed of the exhaust stroke, on the isobvious that the greatest leverage is obtained at the time when the mostpower is available.

To obtain continuity of propulsion, the firing faces 67 are of suchlength that the firing strokes of the pistons overlap, i; e., before thefiring stroke of one, piston'is completed, the firing stroke of anotherpiston is 'i-nitiated. As a result, dead centers are avoided. In thepresent instance, the faces 68 and 70 extend on an arc of 35, and thefaces 67 and'69 extend over an arc of 55. Since the 'piston andcylinderunits are spaced-"30 apart, the firing strokes for adjacentpistons and for'theen'd pistons will-overlap I Suitable means isprovided for holding the cam-rollers45 'continua-lly'in contact with thecam 49. -Preferably.:this--means has a mechanical restoring actioninstead ofa spring action. A spring action is-not entirely satisfactorysince it-may weaken and may-permit knocking. In the present instance,this means comprises a metallic restoring tape 71 (see Figs. 2 and'3)which engages a fixed retaining structure 7 2' and each of the pistons,and whichis suitably secured at its opposite ends. Preferably, the tape71 extends'alternately over rollers 73 of which-oneis mounted in theinner end of each piston, and rollers 74 mounted inthe'structure 72.Seven rollers flt are provided,'andthese-are arranged in an are fallingwell within the inner most'noints'on the cam49. Successive rollers'73earerdisposd' in a line extending'substantially between successivepairs of the roll- 1 sis; 174. fEaclr=of: th-eirollers 73 is rotatablyable. source of lubricant (not shown). "tube 81 opens to said rod 77,and extends rear walls of the oil casing 16. The upper ends of thestandards 75 are arcuate in form and are disposed about the sleeve 57 ofthe cam plate 19a. The rollers 74 are suitably mounted on fixed bearingpins 79 secured between the upper ends of the standards 75.

Suitableoilingmeans is provided. 7 To thisv end, one of the hollowtubular rods 77 opens to a line'80 adapted to be connected to asuittherefrom upwardly and then about the sleeve 57 The upper curved endof the tube 81 is connected through a plurality of branch tubes 82 tothe interior of the bearing pins 7 9. Each of the latter opens to admitoil -where desired.

The ends of the tape 71 are secured to tensioning'means in oppositesides of the casing 10 which preferably are alike in construction, andof which but one Will be described in detail, corresponding parts of theother however,being designated by like referencenumerals. Eachtensioning means (see Figs. 3 and 6) comprises a hollow cylindricalcasing 83 which is removably secured to one side'of the structure 72.and which is inclined upwardly and inwardly at approximately in atangent line to the end roller 74:. The upper end of the casing 83 ispartially closed by a. ring 84 through which the end of the tape 71extends, and the lower end opens next to the side of the casing 10 inline with an opening closed by a plug 85 through which access to thetensioning means may be had. Slidably disposed in the casing 83 is apiston 86 carrying an axial stem 87 having av clamp head 88 in which theend of the tape is secured. In the present instance, the clamp head 88is split longitudinally and has a lateral jaw-shaped opening in its freeend. *The end of the tape is secured about a Wedge 89 in the opening,and the split portions of the head are clamped tightly against the tapeby means of a nut 90 threaded onto the head. The head 88 is arrangedeccentric-ally to the stem 87 so that the latter is in alignment withthe outwardly extending tape. Disposed between the 84 and the piston'86is a coiled spring 91. The tension of the spring 91 may be suitablyadjusted by adjusting the stem'87 in the piston 86. It will be evidentthat the tensioning means serve to give the strip 71 any desiredtension. In normal operation however,the ends of the tape aresubstantially statiohary,- since asone piston gives slack another onetakes up slack to the same extent. As a result the'retaining means hasprimarily a mechanical action and not a spring action. By providing aretaining means of this character, the cam rollers 45 are retainedsecurely and continually against the peripheral faces of the cam 49throughout the complete cycle. As a result, the three pushes and thepull on the piston in the course of each cycle do not result inknocking, i. e., the pressure remains the same with reference to all.hearing parts. This makes it practicable to use ball bearings asdescribed thereby obtaining a smooth even operation, and a low oilconsumption consummation.

Means is provided for actuating the valves 30 and 32 in timed relationto the reciprocation of the pistons. In the present instance, this meanscomprises a pair of timingcams 92 and 93 mounted on the hub 58 of thecam plate 496' The cam 92 is adapted to coact with a plurality ofradially reciprocatory plungers 94 sli dably disposed in bearing sleeves95 formed inthe hub '55 and opening 1 to the periphery of the chamber56. These plungers are connected respectively to aplurality of rods 96which in turn are connected to suitable means 97 for actuating thevalves 30. Similarly, the cam 93 is adapted to actuate a plurality ofplungers 98 slidably disposed in sleeves 99, and connected through rods100 to suitable means 101 for operating the valves 32. The rods 96 and100 are suitably enclosed by hollow tubes 102 and the valve actuatingmechanisms are suitably enclosed by casings 103, one on each cylinderhead 26. The rods 96 and 100 extend in the same radial direction astheir respective cylinders. The exhaust cam 92 has a pair ofdiametrically opposed lugs 104 which are adapted to be movedsuccessively into successive engagement with the plungers 94, and

the intake cam 94 has a pair of diametrically opposed lugs 105 which areadapted to be moved into successive engagement with the plungers 98. Itwill be evident, that as one lug on either cam leaves the last plunger,the

other lug on said cam will engage the first .plunger. The cam 92 ispositioned in ad- 'vance of the lnlet cam 93 so that each exhaust valveopens and closes just ahead of the companion inlet valve 32. r

Means is provided for supplying lubricant or oil to the casings 103 forthe valve actuating mechanlsms. This means comprises an arcuate header106 connected through-a plurality of branch feeder pipes 107 to thecasings 103, and through a pipe 108 to one of ,the tubular rods 77, theother end of said rod being adapted to be connected to a suitable sourceof supply (not shown). Drip oil collecting in the bottom of the casing16 may be withdrawn through a suitable opening 109. Because of theprovision of a cam for actuating the piston and cylinder units, the

valve cams 92 and 93 can be drivendirectly with the cam, therebyeliminating timing gears and various other timing mechanism. As aresult, an extremely simple, eflicient, fool-proof construction isobtained.

The operation will now be'briefiy described. Assuming that the cam 49 isrotating clockwise as appearing in Fig. 1, the piston 36 is near the endof its exhaust stroke, the piston 37 is at the start of its exhauststroke, the piston 38 is on its firing stroke, the piston 39 is near theend of its compression stroke, the piston 40 is atthe start of itscompression' stroke, and the piston 41 is at the start of its inletstroke. As the cam 49 is rotated, each piston will be moved successivelythrough an exhaust stroke, an inlet stroke, a compressionstroke and afiring stroke, and will go through two complete cycles for eachrevolution of the cam, Before the roller on the piston 38 leaves the camsurface 68, the roller on the piston 39 will move onto the cam surface,thereby insuring a continuity of propulsion. A short time'before theroller for the pfston 41 leaves thec am surface 68 of one of the heads63 and 65, the roller for the piston 36 will engage the cam surface 67of the other of the heads 63 and 65. Hence the piston and cylinder unitswill operate in uniformly timed sequence even though grouped in aportion of the'casing.

A variable stroke is obtained; The exhaust strokes are full, therebycompletely expelling the burned gases, and hence insuring com plete andeflicient combustion of the incoming cha rge. Due to the mechanicalrestoring means which effectually retains the pistons in operativerelation to the cam 49, no knocking results and hence'ball bearingscanbe used to advantage. The construction is sim ple and compact, and byreason of the group ing of the piston and cylinder units in the upperportion of the casing, may be conven iently and securely mounted on alarge variety of stationary and moving plants."

I claim as my invention: i I

1. In an internal combustion engine, in combination, a casing, aplurality of piston and cylinder units arranged in peripherally spacedrelation and grouped in a portion of i the periphery of said casing, ashaft, an actu at-ing cam on said shaft,'said cam having plurality ofperipherally spaced heads for moving each piston successively'in anintake stroke, a' compression stroke,-a firing stroke, and an exhauststroke, said heads. being of" unequal length so that said intake strokeand" said exhaust stroke will be substantially longer than saidcompression stroke and said fir ingstroke, certain of said headsbeingjsimilar so asto adapt them to periodically replace each other inoperation so as to operate the pistons of said units continuously,retaining means for holding said pistons in operative relation to saidcam,'means for adjusting said retaining.means,means for oiling saidretaining means, inletand discharge valves'for said units, operatingmechanisms for said valves, and a pair of timing cams rotatable withsaid actuating cam to actuate said valves in timed. relation to themovements of the pistons.

2. In an internal combustion engine, in combination, a casing, aplurality of piston and cylinder units grouped in a portion of saidcasing, a shaft, and an actuating cam on said shaft, said actuating camhaving a plurality of peripherally spaced actuating heads, the number ofheads being a multiple of a number which is the inverse of thatcircumferential portion of said casing occupied by said units, thepistons of said units being operatively related to said cam.

3. In a device of the class described, in combination, a plurality ofpiston and cylinder units, a'rotary cam, means on the pis-- tonsengaging said cam, a stationary retaining structure, a mechanicalretaining member extending alternately in engagement With said pistonsand said retaining structure to hold said means against saidcam.

4. In a device of the class-described, in combination, a piston andcylinder unit, a rotary cam, a cam roller carried by the piston andengaging said .cam, a retaining structure mounted along-side said cam,said retaining structure having a pair of rollers, a roller-mounted inthe inner end of said piston,-and a retaining tape fixed at its ends andextending over said rollers to hold said cam roller in contact with saidcam.

5.111 a device Iof the class described, in combination, a casing, apiston and cylinder unit opening peripherally to said casing, a shaft, acam on said shaft, said piston having .means operatively related to saidcam, a retaining structure comprising a 'pair of vertically spacedstandardsimounted in said casing, and encircling said shaft, a pair ofrollers mounted between said standards and within the innermost circleof revolution of the cam face, .aroller mounted in the inner end of saidpiston, said piston roller being disposed substantially on a linebetween said rollers on said retaining structure, a retaining tapeextending under said retaining rollers and over said piston roller,means for yieldingly securln g the-endsof said tape, and means 7 foradjusting the tension on'said tape.

tons in timed sequence without materially varying the tension in saidmember.

7. In a device of the class described, in combination, a casing, apiston and cylinder unit opening to said casing, a shaft, a double camon said shaft, parts of said cam being disposed on opposite sides ofsaid unit, said piston having a roller and having means operativelyrelated to both parts of said cam, spaced retaining rollers mounted insaid casing at opposite sides of said first mentioned roller and meansfor retaining said first mentioned means and said cam in operativerelation, said last mentioned means extending under said retainingrollers and over said first mentioned roller, means for yieldinglysecuringthe ends of said tape, and means for tensioning said tape.

8. In a device of the class described, in combination, a plurality ofpiston and cylinder units, a rotary cam, means on the pistons engagingsaid cam, a stationary retaining structure, a retaining member extendingalternately in engagement with said pistons and said retainingstructure, and spring means yieldingly securing the ends of said member.

9. In a device of the class described, in combination, a casing, apiston and cylinder unit opening peripherally to said casing, a shaft, acam on said shaft, said cam being double and disposed at opposite sidesof said unit, said piston having means on opposite sides operativelyrelated to said cam, a retaining structure comprising a pair ofvertically spaced standards mounted between said cam parts .in saidcasing, and encircling said shaft, a pair of rollers mounted betweensaid standards and within the innermost circle of revolution ofthecam'face, a roller mounted in the inner end of said piston, aretaining member extending under said retaining rollers and over saidpiston roller, and means for yieldingly securing the ends of saidmember.

10. In a device of the class described, in combination, a retainingstructure comprising a pair of standards, means for holding saidstandards in spaced relation, a plurality of rollers mounted betweensaid standards, a flexible retaining member engaging said rollers andadapted to be flexed between said rollers, and adjustable means fortensioning said member.

In testimony whereof, I have hereunto affixed my signature.

ASA LEE RIGHTENOUR.

